In the conventional microwave oven having a laterally opening door, the role of the switch for stopping oscillation of microwaves for cooking and heating is provided by combination of a door key formed in the door and the door hook formed in the main body, and the latch switch is cut off when the door is opened and the latch switch is turned on when the door is closed, and by turning on the operation switch of the main body, oscillation of microwaves is started. The door key and door hook are composed so as to be engaged with each other as the mutual contact surfaces slide to be engaged with each other, and the sliding surfaces were coated with grease to have lubricity, and the sliding surfaces were prevented from being abraded and worn out during use so that, finally, the latch switch may not fail to work.
For grease application on the sliding surfaces, however, uneven coating tends to occur, and the sliding becomes poor when coating is insufficient, and abrasion of the sliding surfaces may increase, and the microwave oven may fail to work if the door is closed. Besides, as the grease is applied on the sliding surfaces, it may be discolored due to contamination or deterioration in a long course of use, and the appearance becomes poor.